Electrosurgical instruments are well known and widely used in the medical, dental, and veterinarian fields. They offer the capability of precision cutting with electrosurgical currents in the megacycle range using a handpiece with needle, ball, or loop electrodes in a unpolar operating mode, or convenient coagulation using a forceps in a bipolar operating model. Eliman International, Inc. makes available an electrosurgical instrument, Model FFPF, which provides on its front panel connectors for receiving the plug of a unipolar handpiece and a ground or indifferent plate, as well as connectors for receiving the plugs of a bipolar forceps.
There are environments in which the electrosurgical apparatus has to satisfy stringent requirements, including but not limited to simple operation, low cost, energy efficient, safe, and user friendly. in addition, it should provide the capability of precision cutting, coagulating, and homeostasis using high radio-frequency (RF) electrical current, preferably of the order of 3.5-4 mHZ, with 4 mHZ being preferred.
We have found that most of these requirements can be satisfied with low power electrosurgical apparatus that includes only unipolar capability provided that the output power is kept low, preferably at or below about 50 watts. The Model FFPF, whose principles are described in some detail in U.S. Pat. No. 3,730,188 ('188), and further in U.S. Pat. No. 4,463,759 ('759), the contents of both of which are fully incorporated herein by reference, had an output of about 100 watts. Moreover, the Model FFPF used electron tubes, which required high voltages to operate and limited the number of user-friendly features that could be incorporated. Other commercial electrosurgical apparatus, also of the high-voltage, high-power type, employed programmable microcontrollers for producing the different current waveforms needed for surgical tissue cutting, for simultaneous cutting and coagulation, and for coagulation (hemostasis) alone, commonly referred to as the cut, cut/coag, and hemo modes, respectively. U.S. Pat. No. 3,730,188 illustrates in FIGS. 5a, 5b and 5c the three modes above described. As will be noted, the cut mode current waveform is a fully-rectified, filly-filtered, continuous wave (CW) carrier at the RF frequency; the cut/coag mode current waveform is a fully-rectified, unfiltered, continuous wave (CW) carrier at the RE frequency; and the hemo mode current waveform is a half-wave rectified, unfiltered, continuous wave (CW) carrier at the RF frequency. The cut/coag and hemo mode currents are commonly referred to as modulated RF currents. The commercial electrosurgical apparatus of the high-voltage, high-power type employing microcontrollers also are more complex, require more electronic components and assembly, and are thus more expensive than the Model FFPF.